Christopher Reeve's 'Party Trick' Inspired Son's Documentary

Three years after the actor and activist Christopher Reeve died at the age of 52, a new DVD is being released today about Reeve's life after a 1995 horseback riding accident left him paralyzed.

Filmed over a two-year period by Reeve's oldest son, Matthew, "Christopher Reeve: Hope in Motion," is a poignant and sometimes searing look into Christopher and Dana Reeve's family life as Christopher fought to regain mobility and became the voice for others with spinal cord injuries.

Matthew and his sister Alexandra, who are both on the board of the Christopher and Dana Reeve Foundation, joined Diane Sawyer for an exclusive interview on "Good Morning America" to talk about the film.

Matthew Reeve said he decided to make the film after his father unexpectedly moved one of his fingers, more than five years after his injury -- something that Reeve jokingly called his "party trick."

"I was studying film, and it was a matter of timing," Matthew said. "I was visiting home one weekend, and he showed this party trick where he moved his index finger. There was no reported case of anyone with that level of injury having that kind of recovery 5½ years after the accident."

Incredible Progress

The thing that made Christopher Reeve such a powerful advocate was that he refused to accept that he would remain a quadriplegic for life. In fact, he made extraordinary medical progress in the last several years of his life. He was able to breathe without a ventilator for periods of time, take steps in a pool, regain his sense of smell and regain sensation in 70 percent of his body.

Peter Kiernan, the chairman of the Christopher and Dana Reeve Foundation, said that he wished Christopher and Dana were alive today to see the progress being made in treating spinal cord injuries.

"I think when he moved his finger, what he was really doing is pointing the way, and he was showing us that cures are possible, and we are getting people out of chairs today," Kiernan said.

Matthew was 15 when Reeve became paralyzed, and Alexandra, 11. They said it was initially overwhelming.

Tragically, Dana Reeve, who was Matthew and Alexandra's stepmother, died of lung cancer in 2006

"Dana used to liken it to a fall in through the rabbit hole that you're suddenly in this new universe and you have no idea what to expect," Alexandra said. "The amazing thing we learned from Dad and Dana was just to focus on the positive and instead of focus on what we were missing; instead, just look what we did have and what we could do as a family."

Christopher and Dana's son, Will, who was 12 when his father died, is doing very well, Matthew and Alexandra said.

"He's 15 and is thriving in school. He's living with a wonderful family, and we're very close," Alexandra said.

They said the family gained strength from one another other -- especially their dad.

"The moment that surprised me the most, where I saw his strength, was after … he has quite bad news from a doctor," Matthew said. "And you know, he just turned around and, you know, went out for another test to prove that that wasn't the right thing. … He didn't take that as the absolute, and sought out further explanation."